Add metrics for optional features

Many features in the Services code can be disabled via dynamic properties. To decide if a particular feature can be disabled, we need information on how frequently it is used.

1. Go through all configurations and list which features can be disabled.
2. Find a way to measure the usage of each such feature. This will be straightforward in some cases and more complex in others.
3. Add metrics to measure the usage.

Start by reviewing the Services code configurations and identifying features controlled by dynamic properties. For each disableable feature, determine how its usage could be measured, then add metrics covering those cases. Done means the configurations are inventoried and usage metrics exist for every identified optional feature.

Written by the indexing model from the issue text.